Molecular imprinting is the process through which polymers with recognition properties tailored toward a specific template molecule are prepared. This is accomplished by cross-linking a synthetic polymer in the presence of a template molecule. The template molecule is subsequently removed from the resulting cross-linked polymer matrix by washing, leaving behind cavities within the polymer that are complementary in size, shape, and chemical functionality of the template within the polymer. The resulting molecularly imprinted polymers (MIPs) are able to selectively bind to the template molecules in the presence of other molecules. Le Moullec et al., J. Chromatogr. A, 1139, 171-177 (2007); Turiel et al., Anal. Chem., 79, 3099-3104 (2007). This ability makes them ideally suited to a variety of applications, including affinity-based separations, biomimetic sensors, and various organic syntheses. MIPs possess many advantages over established techniques, such as synthetic antibodies, in that they are more chemically and thermally stable, as well as less expensive to produce. Chronakis et al., Macromolecules, 39, 357-361 (2006) However, the molecular template in some MIPs has been shown to degrade with repeated use, decreasing the MIPs' selectivity for its template molecule over time.
Solid phase microextraction (SPME) is a solvent free extraction technique that has obtained widespread popularity in recent years due to it s ease of use, versatility, and robustness. Arthur et al., J. Anal. Chem., 62, 2145-2148 (1990). A SPME device consists of a small amount of an extractive material deposited onto a solid support, typically a fiber. The coated fiber is exposed to the sample of interest, where the analytes that are present are extracted via the extractive material coating. The analytes are then later desorbed from the extractive material coating into an analytical instrument, such as a gas chromatograph, for separation and quantitation. Pawliszyn, J. “Solid Phase Microextraction Theory and Practice”, Chap. 2, 11-42 (1997).
SPME has been applied to a variety of applications, including the analysis of volatile and semi-volatile organic compounds in water samples as well as various in-vitro and in-vivo biological fluids. Musteata et al., J. Anal. Chem., 79, 6903-6911 (2007); Vawdzik et al., J. Liq. Chromatogr. Rel. Technol, 27, 1027-1041 (2004). The versatility of SPME is due primarily to the different types of fiber coatings that can be employed. There are no carbon SPME fibers currently commercially available. Dietz et al., J. Chromatogr. A, 1103, 183-192 (2006).
A number of different methods are described in the literature as having been utilized to fabricate SPME coatings, including sol-gel techniques (Wang et al., J. Chromatogr. A, 893, 157-168 (2000)) and electropolymerization. Bagheri et al., Anal. Chinn. Acta, 532, 89-95 (2005).The inventors recently developed a method to generate SPME fiber coatings via eletrospinning. Specifically, SU-8 2100, a negative photoresist, was electrospun onto stainless steel wires to give a coating comprised of a mat of nanofibers. However, there remains a need for imprinted coatings that exhibited higher selectivity or higher durability than those obtainable using these known techniques.